New XMM-Newton observations of supernova remnants in the Small Magellanic Cloud

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85741 Garching, Germany e-mail: [fwh;wnp]@mpe.mpg.de
² University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW 1797, Australia e-mail: [m.filipovic;e.crawford;a.dehorta;f.stootman]@uws.edu.au
³ Department of Physics, Middlebury College, Middlebury, VT 05753, USA e-mail: winkler@middlebury.edu
⁴ Centre for Astronomy, James Cook University, Townsville QLD, 4811, Australia e-mail: Jeffrey.Payne@jcu.edu.au
⁵ Department of Physics and Astronomy, Swarthmore College, 500 College avenue, Swarthmore, PA 19081, USA

Received: 25 February 2008
Accepted: 20 April 2008

Abstract

Context. A complete overview of the supernova remnant (SNR) population is required to investigate their evolution and interaction with the surrounding interstellar medium in the Small Magellanic Cloud (SMC).

Aims. Recent XMM-Newton observations of the SMC cover three known SNRs (DEM S5, SNR B0050-72.8, and SNR B0058-71.8), which are poorly studied and are X-ray faint. We used new multi-frequency radio-continuum surveys and new optical observations at H_α, [S ii], and [O iii] wavelengths, in combination with the X-ray data, to investigate their properties and to search for new SNRs in the SMC.

Methods. We used X-ray source selection criteria and found one SMC object with typical SNR characteristics (HFPK 334), that was initially detected by ROSAT. We analysed the X-ray spectra and present multi-wavelength morphological studies of the three SNRs and the new candidate.

Results. Using a non-equilibrium ionisation collisional plasma model, we find temperatures kT around 0.18 keV for the three known remnants and 0.69 keV for the candidate. The low temperature, low surface brightness, and large extent of the three remnants indicates relatively large ages. The emission from the new candidate (HFPK 334) is more centrally peaked and the higher temperature suggests a younger remnant. Our new radio images indicate that a pulsar wind nebulae (PWN) is possibly associated with this object.

Conclusions. The SNRs known in the SMC show a variety of morphological structures that are relatively uncorrelated in the different wavelength bands, probably caused by the different conditions in the surrounding medium with which the remnant interacts.